The present invention relates generally to reinforced objects, especially reinforced elongated objects such as, for example, shaft-based sporting implements.
Not only due to their geometry, but also due to the often extreme conditions in which they are used, elongated objects have a tendency to fracture, especially transverse to their length. This is often the case when, for example, the elongated object comprises a shaft-based sporting implement. A number of shaft-based sporting implements experience extremely stressful conditions of use. Lacrosse sticks, hockey sticks, golf clubs, tennis and similar rackets, skis, baseball and similar bats, sailboat and similar masts, paddles, and polo mallets are examples of such shaft-based sporting implements.
Not surprisingly, many ways of increasing the strength of shaft-based sporting implements, including those mentioned, have been explored. Sporting implements lacking necessary strength for their purpose can result in competitive disadvantages when, for example, the shaft-based sporting implement breaks during competition. A broken shaft-based sporting implement can also pose a safety hazard to the player using the implement and others. However, when improving the strength of shaft-based sporting implements, competitive disadvantages, such as decreased flexibility and maneuverability, can also be an undesirable consequence.
One way of increasing the strength of shaft-based sporting implements focuses on the type of material used in the implement. For example, a Princeton University student and his father developed the first titanium lacrosse shaft prototypes in 1992. They were found to be twice as strong and half the weight of aluminum or wood. The student and his teammates used the prototypes en route to the lacrosse national championship that year. Warrior Lacrosse, which is now one of the leading manufacturers in the lacrosse industry, was then founded based on that discovery.
U.S. Pat. No. 6,939,257 describes longitudinal reinforcing fibers contained within the outer one of at least two composite layers comprising a hockey shaft. The relative proportion of the reinforcing fibers, whether they be glass or carbon, and the binding material is described as being substantially constant at the different portions of the cross-section of the layer in which they are contained. The longitudinally reinforced fiber layer may be formed by, for example, pultrusion of the fibers. Particularly disclosed is the use of carbon fibers (e.g., those designated in the Figures by numeral 5a) on corners of a rectangular shaft for enhancing impact resistance of the shaft of a hockey stick. Also disclosed is application of an outer layer of reinforcement material (e.g., one containing aramid fibers) to provide protection for the longitudinal reinforcing fibers against blows. The outer layer of reinforcement material can be positioned only at the corners of the rectangular shaft when increased impact resistance is desired.
U.S. Pat. No. 7,008,338 discloses a hockey stick. Further described is a hockey stick blade having a lightweight core and an outer layer formed of a wood laminate, injection-molded plastic, or other material. The outer layer can include inserts such as metal or wood inserts molded, glued or co-formed therewith.
U.S. Patent Publication No. US-2008-0213490 relates to increasing strength of an article by using braid reinforcement. This patent publication discloses resin compositions that facilitate improved impregnation of intermediate pre-braided fiber forms when forming braid-reinforced composites. The braid-reinforced composites can be used in a variety of applications, including wind surfing masts, snow boards, water skis, snow skis, wake boards, sail masts, boat hulls, hockey sticks, golf shafts, bicycle components, baseball bats, tennis and other racquets, and kayak and canoe paddles.
Another way of increasing the strength of shaft-based sporting implements focuses on geometry of the implement. As an example of this approach, U.S. Pat. No. 4,361,325 discloses corner reinforcements on shafts. Disclosed is an elongated, hollow, game stick handle for hockey sticks, or the like, which is formed from a plastic material. The handle has a substantially rectangular cross-section. The outer and inner surfaces of the handle are arcuately shaped for increased strength and improved fracture resistance. The side walls and corners of the handle are of non-uniform thickness, with the minimum wall thickness of the shorter sides being greater than the minimum wall thickness of the larger sides. The maximum wall thickness of the corners is greater than the minimum wall thicknesses of the shorter or larger sides.
U.S. Pat. No. 4,361,325 also discusses how reinforcing ribs have been placed in the interior of a hockey stick shaft to provide desired reinforcement, making the hockey stick more durable. Use of internal rods in shaft-based sporting implements is also discussed in U.S. Pat. No. 6,113,508, which discloses the use of a stiffening rod in cavities of various sporting implements to permit the user to adjust the stiffness thereof. Some embodiments disclose the use of multiple cavities or chambers spaced across the sporting implement (e.g., ski or snow board) to accommodate stiffening rods. As such, each of the pieces of sports equipment discussed therein is capable of being split into multiple sections, each with its own adjustable flexibility and stiffness. The stiffening rods are described as being capable of being stepped or tapered and not necessarily of uniform dimension.
U.S. Pat. No. 7,108,618 discloses methods and apparatus for repairing fractured, hollow-shafted hockey sticks. In one aspect, a shaft extension member for repairing or adjusting the length of hockey shaft is disclosed. Either or both of the shaft and shaft extension member can be made of composite material. The shaft extension member can have internal reinforcement structures of various geometries for increased strength.
U.S. Pat. Nos. 7,285,063 and 7,326,135 disclose hockey stick shafts having a cross-section and other properties varying along a length thereof. The varying cross-section defines selected regions of optimized grip for the hands of a player and of optimized rigidity and resistance in torsion of the shaft. The shaft may comprise reinforcements, such as longitudinally oriented high tensile strength wires and fibers on opposite surfaces, as a way to increase rigidity of the shaft and hold broken pieces of the shaft together in the event of a transverse sectional breakage thereof.
Exterior add-ons have also been used on some shaft-based sporting implements for certain purposes. For example, U.S. Pat. No. 6,500,079 discloses a variable hand placement sports equipment handle, such as a lacrosse stick handle, hockey stick handle, or field hockey stick handle, which includes a shaft and at least one overlay attached to the shaft at a location of frequent hand placement. The overlays are specially located and structured to provide the shaft with structural and tactile features that correspond to and accommodate the way in which a player moves his hands along the shaft and grips the shaft. The structural and tactile features, such as ribs, grooves, and hourglass and conical shapes, are located on the shaft to enhance a player's control of the shaft when performing various skills. In one embodiment, an overlay (that could be smooth or consist of latitudinal ribs) extends the entire length of a shaft to completely encase the shaft and provide an end cap on the shaft. By encasing the entire length of the shaft, the shaft is said to be better protected and able to be constructed of a thinner wall thickness. The overlays are described as being made of a material that is preferably soft, pliable, deformable, and tacky in places, so as to provide a player with a better hold on the handle.
U.S. Pat. No. 7,108,619 discloses a hockey stick handle that has an inner shaft member of carbon fiber or other material, which provides flexing characteristics, and an outer tubular member in which the inner shaft member is fitted. The outer tubular member provides protection for the inner shaft member by facilitating the advantages of a carbon fiber handle, but with a reduced tendency of breakage.
An alternative method for reducing the tendency of composite hockey sticks to break is described in U.S. Pat. No. 7,128,669. Disclosed therein is a composite hockey stick shaft having an elongated body and four side wall members. At least one side wall member comprises an inner layer of fibers disposed within a matrix material, a layer of viscoelastic material anchored onto the outside surface of the inner layer, and an outer layer of fibers disposed within the matrix material. The outer layer is disposed on and abuts the outside of the layer of viscoelastic material.
Each of the above-described methods of increasing the strength of shaft-based sporting implements has its advantages and disadvantages. Nevertheless, further ways of increasing the strength of a variety of objects, including various shaft-based sporting implements, are desired.